Organization and Basis of Presentation (Schedule of Cash and Cash Equivalents) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Line Items]
Cash and Cash Equivalents, at Carrying Value	$ 421	$ 358
Restricted Cash and Cash Equivalents, Current	149	138
Restricted Cash and Cash Equivalents, Noncurrent	9	9
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	579	505	$ 1,022	$ 541
Progress Energy [Member]
Cash and Cash Equivalents [Line Items]
Cash and Cash Equivalents, at Carrying Value	20	40
Restricted Cash and Cash Equivalents, Current	13	40
Restricted Cash and Cash Equivalents, Noncurrent	6	7
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	39	87	58	110
Duke Energy Florida [Member]
Cash and Cash Equivalents [Line Items]
Cash and Cash Equivalents, at Carrying Value	6	13
Restricted Cash and Cash Equivalents, Current	13	40
Restricted Cash and Cash Equivalents, Noncurrent	0	0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 19	$ 53	$ 21	$ 69